The present invention relates to a transmission method between a card reader/writer and an IC card.
A processing system has been developed wherein half-duplex data transmission is performed between a card reader/writer and an IC card. In this processing system, a control program in the IC card is started in response to a reset signal from the card reader/writer The IC card receives and decodes an instruction supplied from the card reader/writer to execute corresponding processing. Thereafter, the IC card sends the processed result as response data to the card reader/writer. In this case, the card reader/writer must recognize a transmission protocol of the IC card.
However, different IC cards normally have different transmission protocols. After it is recognized that the reset state is canceled by the reset signal, the IC card sends initial response data called "Answer to Reset" in order to signal the transmission protocol and the like to the card reader/writer. The answer to reset signal consists of 8 through 32 bytes and includes transmission protocol data. The transmission protocol data includes, e.g., a data transmission rate, data indicating whether or not a parity bit is affixed, data indicating whether parity check is performed or even/odd numbered parities, data indicating positive or negative logic, and the like. Thereafter, the IC card awaits input instruction data. In this case, a time between when the initial response data is sent and when an instruction data waiting state is established depending on the type of IC card. However, there is no means for detecting this difference in time. Therefore, when the card reader/writer that designates processing to the IC card sets a time interval from when initial response data is received until next instruction data is sent, a maximum time interval for respective types of IC cards is set. Because the maximum time interval is used, an appropriate most efficient send timing of instruction data for the respective types of IC card cannot be obtained.